Long-term changes in body potassium concentration and dose from 40K for a Japanese adult male group

Total body potassium has been measured for a Japanese adult male group using two whole-body counters. The total body potassium data were analyzed to present the longitudinal data on body potassium concentration in aging individuals. The data for each individual showed that potassium concentration decreased linearly with age from 30 y to 60 y of age. The average decrease rate was -0.0154 +/- 0.0049 g K kg body wt(-1) y(-1). On the other hand, a subject group for each of the 23 years (1975-1998) of the study was divided into three age groups. The same age groups were followed with the course of time to analyze changes in potassium concentration due to other factors besides age. The follow-up study of the same age groups indicated that the average potassium concentration decreased with the course of the 23-y study and that the decrease was due to other factors besides age. The decrease in the average potassium concentration for study subjects is the major cause of the decrease in the average annual dose from K-40. The average annual dose for subjects aged 30-59 y was 194 mu Gy in 1975, changing to 166 mu Gy in 1998. The decrease in the average annual dose was about 14% over the 23-y study period.